[Embolotherapy: principles and indications]

Application of 4D printing and bioprinting in cardiovascular tissue engineering

Cardiovascular diseases have remained the leading cause of death worldwide for the past 20 years. The current clinical therapeutic measures, including bypass surgery, stent implantation and pharmacotherapy, are not enough to repair the massive loss of cardiomyocytes after myocardial ischemia. Timely replenishment with functional myocardial tissue via biomedical engineering is the most direct and effective means to improve the prognosis and survival rate of patients. It is widely recognized that 4D printing technology introduces an additional dimension of time in comparison with traditional 3D printing. Additionally, in the context of 4D bioprinting, both the printed material and the resulting product are designed to be biocompatible, which will be the mainstream of bioprinting in the future. Thus, this review focuses on the application of 4D bioprinting in cardiovascular diseases, discusses the bottleneck of the development of 4D bioprinting, and finally looks forward to the future direction and prospect of this revolutionary technology.

[Radiological embolization procedures in acute gastrointestinal, peritoneal and muscular hemorrhage]

BACKGROUND

Treatment of acute hemorrhage is particularly challenging due to its sudden onset and the fact that it is often life-threatening. Potential causes include bleeding ulcerations of the gastrointestinal tract or tumor bleeding, but acute bleeding can also occur spontaneously or be traumatic, iatrogenic, or inflammatory.

OBJECTIVE

To demonstrate the basic principles of catheter embolization, as well as various embolic materials and their properties.

RESULTS

Today there are a wide range of embolization materials available. Ultimately the duration and extent of the desired occlusion are decisive when selecting an embolic material. Mechanical occlusion devices, particulates, and liquid embolic agents are available.

CONCLUSION

Irrespective of the wide range of different etiologies, radiological embolization therapy is a very safe treatment option in cases of computed tomographic evidence of active hemorrhage. Ultimately, the interventionalist's comprehensive knowledge of the relevant characteristics is crucial for the success of therapy.

Endovascular Management of a Giant High-Flow Lower Limb Arteriovenous Malformation

PURPOSE

High-flow arteriovenous malformations (AVMs) may pose a challenge for endovascular treatment due to high-flow rates. Incomplete treatment, recurrence, or even worsening can occur if a proper management is not performed. We report a case successfully treated with endovascular therapy.

CASE REPORT

A 37-year-old male was referred to our hospital with a soft tumor in the left thigh, limb asymmetry and associated pain. Doppler ultrasound and magnetic resonance imaging showed an extensive high-flow AVM with a venous aneurysm of 40 mm diameter. Diagnostic angiography identified multiple feeding vessels from the profunda femoris and superficial femoral arteries. Two endovascular interventions were performed within 1 month, combining afferent vessel embolization and percutaneous thrombin injection into the nidus, to exclude the AVM. Two-year imaging follow-up revealed thrombosis of the malformation. The patient remained asymptomatic with normal thigh diameter. No complications were documented in any of the sessions.

CONCLUSION

Endovascular therapy could be a safe and effective option for AVM as long as it includes not only feeding vessels embolization but also complete occlusion of the nidus.

Review of the Development of Methods for Characterization of Microspheres for Use in Embolotherapy: Translating Bench to Cathlab

Therapeutic embolotherapy is the deliberate occlusion of a blood vessel within the body, which can be for the prevention of internal bleeding, stemming of flow through an arteriovenous malformation, or occlusion of blood vessels feeding a tumor. This is achieved using a wide selection of embolic devices such as balloons, coils, gels, glues, and particles. Particulate embolization is often favored for blocking smaller vessels, particularly within hypervascularized tumors, as they are available in calibrated sizes and can be delivered distally via microcatheters for precise occlusion with associated locoregional drug delivery. Embolic performance has been traditionally evaluated using animal models, but with increasing interest in the 3R's (replacement, reduction, refinement), manufacturers, regulators, and clinicians have shown interest in the development of more sophisticated in vitro methods for evaluation and prediction of in vivo performance. Herein the current progress in developing bespoke techniques incorporating physical handling, fluid dynamics, occlusive behavior, and sustained drug elution kinetics within vascular systems is reviewed. While it is necessary to continue to validate the safety of such devices in vivo, great strides have been made in the development of bench tests that better predict the behavior of these products aligned with the principles of the 3R's.

[Interventional radiology in the head and neck region]

In interventional neuroradiology, endovascular embolization represents an important and helpful tool in the treatment of multiple head and neck diseases. These interventional procedures may be performed with curative intent, to reduce the surgical risk within a multimodal treatment concept, or to improve or at least maintain a good quality of life within a palliative therapy concept. In addition to a good understanding of disease pathology, knowledge of vascular anatomy, including collateral vessels and dangerous extracranial-intracranial anastomoses, is essential for successful treatment, as is implementation of an established technique using appropriate material. Indications for endovascular embolization are i. otherwise unmanageable bleeding (caused by e. g., trauma, vascular malformation, or tumor), ii. reduction of perioperative bleeding by preoperative embolization in case of a hypervascularized tumor, iii. selective induction of tumor necrosis by palliative embolization to enhance local tumor control. Major complications such as stroke, loss of vision, and cranial nerve palsy are mostly due to a lack of preinterventional evaluation. Regarding neurological deficits, interventions within the supply region of the external carotid artery have a complication rate below 1%.

[Neuroradiologic diagnostic and interventional procedures for diseases of the skull base]

Besides image-guided biopsy techniques, the emphasis in the interdisciplinary cooperation between head and neck surgery and neuroradiology is on vessel-occluding and preserving measures. Knowledge of dangerous anastomoses between extracranial and intracranial vessels is crucial. The principles of vessel-occluding procedures including materials are presented and illustrated with case examples. Embolization of glomus tumors or epistaxis and preoperative permanent vessel occlusion techniques are demonstrated as well as vessel-preserving therapies, such as placement of covered stents for improving tumor resectability or after iatrogenic laceration of the internal carotid artery.

[C-arm CT for planning and guidance of extrahepatic embolizations]

Interventional radiological vascular embolizations are complex procedures that require exact imaging of the target region to facilitate safe and effective treatment. The purpose of this paper is to present the technique and feasibility of flat detector C-arm computed tomography (C-arm CT) for control and guidance of extrahepatic abdominal embolization procedures. C-arm CT images can provide important information on both vascular and cross-sectional anatomy of the target region, help in determining therapy endpoints and provide follow-up during and immediately after the abdominal interventions.The cases presented demonstrate that C-arm CT images are beneficial for abdominal embolization procedures and facilitate precise treatment.

[Arterial embolization of hepatic metastases from neuroendocrine tumors]

Neuroendocrine tumors are slowly growing neoplasms and 75% of patients already present with hepatic metastases at the time of diagnosis. Size and growth of liver metastases is of prognostic value. Due to arterial vascularization of metastases, transarterial embolization (TAE) is a suitable procedure, which can also be combined with chemotherapeutic agents. Indications for embolization or chemoembolization (TACE) are growth of liver metastases or inadequate symptom control. The majority of patients show clinical improvement and partial remission can be achieved in 50% of cases with 5-year survival rates of 50-60%. Response rates, survival or complications are not dependent on the embolization technique (TAE or TACE). Embolization is usually performed in several sessions depending on individual tumor stage and disease progression. Embolization is a cost-effective procedure and is included in the treatment algorithm of international guidelines. Therefore, evaluation of new embolization therapies must be evaluated in randomized controlled studies.